1. Field of the Invention
The present invention relates to an apparatus, a method and a computer program product for recognizing and identifying a three-dimensional object.
2. Description of the Related Art
Jpn. Pat. Appln. KOKAI Publication No. 11-265452, for example, discloses a method for recognizing/identifying a three-dimensional object using images obtained by photographing the object in various directions (hereinafter referred to as “conventional method”).
In the conventional method for using a subspace method, a dictionary, in which a three-dimensional object is represented in the form of subspaces, is created based on the vectors extracted from a plurality of images taken from the three-dimensional object in advance. Similarly, a subspace is formed from the vectors extracted from input images taken by a camera. The angle between each subspace in the dictionary (hereinafter referred to as “dictionary subspace”) and the subspace of the input images (hereinafter referred to as “input subspace”) is measured. If a certain dictionary subspace forms a smallest angle with respect to the input subspace, it is considered to have the highest similarity (=the identified object).
In the actual recognition process, the eigenvalue λi (i=natural number) of the matrix defined using the basis vectors of an input subspace and a dictionary subspace is obtained, and is used to compute the similarity corresponding to the angle θi (i=natural number) between the input subspace and the dictionary subspace. More specifically, the highest eigenvalue λ1 itself, or the ratio r of the highest eigenvalue to the second highest eigenvalue λ2, r=λ2/λ1, is used as a similarity.
However, if the highest eigenvalue λ1 itself, or the ratio r of the highest eigenvalue to the second highest eigenvalue λ2, r=λ2/λ1, is used as a similarity, there is a case where an actual three-dimensional object cannot be discriminated from its picture. This is because if an image of the picture is identical to an image registered in a dictionary, the actual object cannot be discriminated from the picture.
This raises a serious problem, especially when security system based on face recognition is concerned. Security system may easily be compromised if a picture of a person is presented instead of the person.